Charm physics and XYZ states at BESIII Evgeny BOGER JINR Dubna On - - PowerPoint PPT Presentation

Charm + XYZ at BES-III

Charm physics and XYZ states at BESIII

FAIRNESS2016

• Feb. 15, 2016

Evgeny BOGER JINR Dubna On behalf of BESIII collaboration

Charm + XYZ at BES-III

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Outline

• BESIII experiment
• Charm physics
• Recent XYZ results

Charm + XYZ at BES-III

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BEPC II

BES-III LINAC

Beam energy: 1 - 2.3 GeV Beam current: 0.91A

8×1032cm−2 s−1

Achieved luminocity:

e+e-

Charm + XYZ at BES-III

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BESIII Detector

1T superconducting magnet EMC:

• CsI crystals
• Energy resolution: 2.5%@1GeV
• Spatial resulution: 6mm

MDC:

• Spatial resulution: σxy = 120μm
• Momentum resolution: 0.5%@1GeV
• dE/dx resolution: 6%

Muon ID

• 8 layers of RPC inside the yoke

(9 in endcaps)

TOF

• Two layers of scintillator
• Time resolution:

90 ps (barel), 120 ps (endcaps)

Charm + XYZ at BES-III

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BESIII Data Sample

• Data taking since 2008
• World largest sample in e+e-

: J/ψ, ψ(2S), ψ(3770), Y(4260) →

Image from S. Spataro – Spectroscopy in the charm range: from BESIII to PANDA

Charm + XYZ at BES-III

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Charm physics at BESIII: Motivation

• Unitarity test of CKM matrix: measuring |Vcs|

and |Vcd|

• LQCD calibration: fD->K/π(q2) and other FFs, fD(s)+

decay constant

• New Physics: fjnding evidence of CP violation,

rare decays, signifjcant deviations from CKM unitarity or from LQCD calculations

• Providing inputs for b-physics

Charm + XYZ at BES-III

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Charm physics: data samples

2.93 fb

−1@3.773GeV for D 0 D 0 , D + D

• 0.48 fb

−1@4.009 GeV for Ds + Ds

• 0.57 fb

−1@ 4.599GeV for Λc +Λc

Charm + XYZ at BES-III

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Analysis Technique

• Pure DD fjnal state, no

additional hadrons

• «Tag» D-meson is fully

reconstructed

• Signal is searched at the

recoiling side

Example: e+e- → ψ(3770) D → D

• Tag selection based on two

variables:

• Tag yeild is obtained by fjtting

mBC

Δ E=E D−Ebeam mBC=√ Ebeam

2

−| ⃗ pD|

Charm + XYZ at BES-III

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Analysis of D+ → K-π+e+νe

• Branching fractions

arxiv:1512.08627

BESIII preliminary

• Amplitude analysis

–

Fitted fractions (S+P)

BESIII preliminary

Nsig = 18262 background level: 0.7%

Cont.

• S-wave phase measurement

–

Consistent with LASS parameterization

• Model-independent helicity basis FF study

–

Consistent with the PWA solution and CLEO-c results

BESIII preliminary

Charm + XYZ at BES-III

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PWA of D+ → K-π+e+νe

BESIII preliminary BESIII preliminary

Projections of data and PWA solution MC (S+P)

arxiv:1512.08627

First measurement

• f SPD V pole mass

Charm + XYZ at BES-III

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D+ → K-π+e+νe S-wave phase

BESIII preliminary

S-wave phase δs is independently fjtted in 12 mKπ bins

Model-independent measurement of BESIII are consistent with its result from amplitude analysis within 1σ .

Blue dots: BESIII model-independent measurement Red and dotted lines: predicted by fjt based on LASS parameterization Green dots: BABAR model-independent measurement with S+D+P

arxiv:1512.08627

Charm + XYZ at BES-III

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Model-Independent Measurement of Form Factors

BESIII preliminary

Red dots : BESIII model-independent measurement Black dots : CLEO model-independent measurement Blue Line : BESIII result from amplitude analysis (it's not the fjt!)

• Events located in the K* window [0.8,1]

GeV/c2, are used to measure the form factors by a Projective Weighting Technique [Phys. Rev. D 81, 112001 (2010)].

• Signal is assumed to be composed of K*

and a non-resonant S-wave.

• Helicity basis form factors include:
• P-wave related: H±(q2)
• S-wave related: h0(q2)
• Five weighted q2 histograms are built.

Weight is assigned to each event based on kinematic variables.

• Form factors are independently computed

in each bin.

• The model-independent measurements

are generally consistent with CLEO-c and with SPD-model results from amplitude analysis

arxiv:1512.08627

Charm + XYZ at BES-III

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Study of D0 → K-/π- e+ νe

PRD92 (2015) 072012

D0 → K- e+ νe D0 → π- e+ νe

Using CKMFitter |Vcs(d)| as input Measure |Vcs(d)| × f+

K(π)

Charm + XYZ at BES-III

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Study of D+ → ωe+νe and search for D+ → ϕe+νe

PRD 92, 071101(R) (2015)

D+ → ωe+νe D+ → ϕe+νe

data

First D+ → ωe+νe form factor measurement Form factor ratios: Branching ratios:

Charm + XYZ at BES-III

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Observation of D+ → ωπ+ and evidence for D0 → ωπ0

arXiv:1512.06998

D+ → ωπ+ D0 → ωπ0

D+ → ωπ+ is singly Cabibbo-suppressed

5.5σ 4.1σ

BESIII preliminary BESIII preliminary BESIII preliminary

Charm + XYZ at BES-III

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Absolute BF for Λ+

c →Λ e+νe

PRL115(2015)221805 109.4±10.9

ST First direct measurement

BF(Λc

+→Λ e+νe)=(3.63±0.38±0.20)%

Theoretical predictions: 1.4% to 9.2%

BF(Λc

+→Λ e+νe)

Previous indirect measurements: (2.9±0.5)%

Charm + XYZ at BES-III

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XYZ States

“XYZ” states:

• Charmonium (cc) in the fjnal

state

• Do not fjt into the

conventional quark model of charmonium

Image from S. Olsen Front. Phys. 10, 101401 (2015)

Charm + XYZ at BES-III

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Exotic Hadrons

• Conventional hadrons: 2 or 3 quarks
• QCD doesn't forbid exotic hadrons:
• Glueball (no quarks)
• Hybrid (quarks + excited gluon)
• Multiquark (N > 3)
• Hardon molecule (bound state of hadrons)

Charm + XYZ at BES-III

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BESIII Data Sets

Charm + XYZ at BES-III

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Zc states at BESIII

Zc(3900)+

PRL110, 252001[2013]

Zc(3900)0

PRL 115, 112003 (2015)

Neutral partner is found in e+e- → π+π-J/ψ

Charged charmonium-like state

• M = (3899.0 ± 3.6 ± 4.9) MeV/c2
• Γ = (46 ± 10 ± 20) MeV/c2
• Signifjcance > 8σ
• M = 3894.8 ± 2.3 ± 3.2 MeV/c2
• Γ = 29.6 ± 8.2 ± 8.2 MeV/c2
• Significance = 10.4σ

Isospin triplet

Charm + XYZ at BES-III

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Zc states at BESIII

Zc(3885)+

Found in e+e- → π+(DD*)- @ 4.26 GeV (ST) confjrmed @ 4.23, 4.26 GeV (DT)

Image from XYZ states at the BESIII experiment by Gianfranco Morello

• M = 3881.7 ± 1.6 ± 2.1 MeV/c2
• Γ = 26.6 ± 2.0 ± 2.3 MeV/c2
• Signifjcance > 10σ
• Angular distribution consistent with

JP=1+

Zc(3885)0

e+e- → π0(DD*)0

• M = 3885.7 +4.3
• 5.7 ± 8.4 MeV/c2
• Γ = 35 +11
• 12 ± 15 MeV/c2
• Signifjcance > 12σ

Isospin triplet

PRL 115, 222002 (2015) PRD 92, 092006 (2015)

Charm + XYZ at BES-III

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Zc states at BESIII

PRL 113, 212002(2014) PRL 111, 242001(2013)

Zc(4020)+ Zc(4020)0

e+e- → π+π-hc e+e- → π0π0hc

• M = (4022.9 ± 0.8 ± 2.7) MeV/c2
• Γ = (7.9 ± 2.7 ± 2.6) MeV/c2
• Signifjcance > 8.9σ
• M = 4023.9 ± 2.2 ± 3.8 MeV/c2
• Γ fjxed to Zc(4020)+
• Signifjcance: 5σ

Isospin triplet

Charm + XYZ at BES-III

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Zc states at BESIII

PRL112, 132001 (2014)

Zc(4025)+

In e+e- → π+(D*D*)-

Zc(4025)0

• M = (4026.3 ± 2.6 ± 3.7) MeV/c2
• Γ = (24.8 ± 5.6 ± 7.7) MeV/c2
• Signifjcance > 10σ
• M = (4025.5+2.0
• 4.7 ± 3.1) MeV/c2
• Γ = (23.0 ± 6.0 ± 1.0) MeV/c2
• Signifjcance > 5.9σ

Isospin triplet

Charm + XYZ at BES-III

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Zc states at BESIII: Summary

Table by Guangshun Huang «Overview of the BESIII Experiment» 4th LNF Workshop on Cylindrical GEM Detectors

Charm + XYZ at BES-III

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X States at BESIII

e+e- → γX(3872) X(3872) → π+π-J/ψ X(3872)

• M = 3871.9 ± 0.7 ± 0.2 MeV/c2
• Γ < 2.4 MeV/c2 @ 90% C.L

6.3σ

Y(4260) → γX(3872) decay was recently observed at BESIII

PRL 112, 092001 (2014)

X(3823)

PRL 115, 011803 (2015)

6.2σ

• M = 3821.9 ± 1.3 ± 0.7MeV/c2
• Consistent with ψ(13D2)

X(3823) observed in e+e- → π+π-X(3823) X(3823)→γχC1

Charm + XYZ at BES-III

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Y States

• M = 4230 ± 8 ± 6 MeV/c2
• Γ = 38 ± 12 ± 2 MeV
• Signifjcance > 9σ

Y(4230)

e+e- → ωχc0

PRL, 114, 092003

Possible interpretations:

• Tetraquark
• ψ(4S)
• threshold effect?

4.23 GeV 4.26 GeV

Charm + XYZ at BES-III

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Summary

• Charm physics

– Semileptonic analyses (hadronic FF and decay

constant)

• D+ → K-π+e+νe, D0 → K-/π- e+ νe , D+ → ωe+νe
• Recent progress in XYZ:

– Neutral Zc partners are found:

• Zc(3900)0, Zc(3885)0, Zc(4020)0, Zc(4025)0

–

ψ(13D2) (X(3823)) is observed

–

Y(4230)

• BESIII continues to take data

– More interesting results are expected soon